Serializers 序列化组件

一 Django下的序列化

二 DRF序列化的方法

三 ModelSerializer

一 Django下的序列化

from django.shortcuts import render, HttpResponse

# Create your views here.
import json
import datetime
from app01 import models
from django.views import View

class BooksView(View):
    def get(self, request):
        book_list = models.Book.objects.values("id", "title", "chapter", "pub_time", "publisher")
        book_list = list(book_list)
        # 如果我们需要取外键关联的字段信息 需要循环获取外键 再去数据库查然后拼接成我们想要的
        ret = []
        for book in book_list:
            pub_dict = {}
            pub_obj = models.Publish.objects.filter(pk=book["publisher"]).first()
            pub_dict["id"] = pub_obj.pk
            pub_dict["title"] = pub_obj.title
            book["publisher"] = pub_dict
            ret.append(book)
        ret = json.dumps(book_list, ensure_ascii=False, cls=MyJson)
        return HttpResponse(ret)


# json.JSONEncoder.default()
# 解决json不能序列化时间字段的问题
class MyJson(json.JSONEncoder):
    def default(self, field):
        if isinstance(field, datetime.datetime):
            return field.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(field, datetime.date):
            return field.strftime('%Y-%m-%d')
        else:
            return json.JSONEncoder.default(self, field)

from django.shortcuts import render, HttpResponse
from django.views import View
from app01 import Book
from django.core import serializers


# 能够得到我们要的效果 结构有点复杂
class BooksView(View):
    def get(self, request):
        book_list = Book.objects.all()
        ret = serializers.serialize("json", book_list)
        return HttpResponse(ret)

二 DRF序列化的方法

首先我们准备一个简单的表结构

from django.db import models

# Create your models here.


class Book(models.Model):
    title=models.CharField(max_length=32)
    price=models.IntegerField()
    pub_date=models.DateField()
    publish=models.ForeignKey("Publish")
    authors=models.ManyToManyField("Author")
    def __str__(self):
        return self.title

class Publish(models.Model):
    name=models.CharField(max_length=32)
    email=models.EmailField()
    def __str__(self):
        return self.name

class Author(models.Model):
    name=models.CharField(max_length=32)
    age=models.IntegerField()
    def __str__(self):
        return self.name

开始

序列化

# url
from django.conf.urls import url
from django.contrib import admin
from app01 import views

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^publishes/$', views.PublishView.as_view(),name="publish")
]

# 视图
from .models import *
from rest_framework.views import APIView
from rest_framework import serializers

  # 为queryset,model对象做序列化
  class PublishSerializers(serializers.Serializer):
　　　　name = serializers.CharField()
　　   email = serializers.CharField()

class PublishView(APIView):
    def get(self,request):
        # 序列组件
        publish_list = Publish.objects.all()
        ps = PublishModelSerializers(publish_list, many=True)
        return Response(ps.data)

注意  上面是对一张单表进行操作 比较简单，接下来我们对一个有外键关系的表进行操作

外键关系的序列化

看最上面的book表

# url
from django.conf.urls import url
from django.contrib import admin
from app01 import views

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^books/$', views.BookView.as_view(),name="books"),
]

from rest_framework.views import APIView
from rest_framework.response import Response
from .models import Book
from rest_framework import serializers

class BookSerializers(serializers.Serializer):
    title=serializers.CharField(max_length=32)
    price=serializers.IntegerField()
    pub_date=serializers.DateField()
　　# 对于一对一的字段 可以使用 souce来取值 但是对于 ManyToMany 就不好使了 我们用下面的方法
    publish=serializers.CharField(source="publish.name")
    #authors=serializers.CharField(source="authors.all")
　　# 解决 ManyToMany字段
    authors=serializers.SerializerMethodField()
    def get_authors(self,obj):
        temp=[]
        for author in obj.authors.all():
            temp.append(author.name)
        return temp


class BookViewSet(APIView):

    def get(self,request,*args,**kwargs):
        book_list=Book.objects.all()
        bs=BookSerializers(book_list,many=True)
        return Response(bs.data)

# 这种方法又特别的麻烦 就有下面的  ModelSerializer

反序列化

当前端给我们发post的请求的时候~前端给我们传过来的数据~我们要进行一些校验然后保存到数据库~

这些校验以及保存工作，DRF的Serializer也给我们提供了一些方法了~~

首先~我们要写反序列化用的一些字段~有些字段要跟序列化区分开~~

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    w_chapter = serializers.IntegerField(write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    user = UserSerializer(many=True, read_only=True)

    users = serializers.ListField(write_only=True)
    publisher_id = serializers.IntegerField(write_only=True)

    def create(self, validated_data):
        book = Book.objects.create(title=validated_data["title"], chapter=validated_data["w_chapter"], pub_time=validated_data["pub_time"],                                  publisher_id=validated_data["publisher_id"])
        book.user.add(*validated_data["users"])
        return book

class BookView(APIView):
    def get(self, request):
        book_list = Book.objects.all()
        ret = BookSerializer(book_list, many=True)
        return Response(ret.data)

    def post(self, request):
        # book_obj = request.data
        serializer = BookSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.validated_data)
        else:
            return Response(serializer.errors)

更新

class BookSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    title = serializers.CharField(max_length=32)
    CHOICES = ((1, "Linux"), (2, "Django"), (3, "Python"))
    chapter = serializers.ChoiceField(choices=CHOICES, source="get_chapter_display", read_only=True)
    w_chapter = serializers.IntegerField(write_only=True)
    pub_time = serializers.DateField()

    publisher = PublisherSerializer(read_only=True)
    user = UserSerializer(many=True, read_only=True)

    users = serializers.ListField(write_only=True)
    publisher_id = serializers.IntegerField(write_only=True)

    def create(self, validated_data):
        book = Book.objects.create(title=validated_data["title"], chapter=validated_data["w_chapter"], pub_time=validated_data["pub_time"],
                                   publisher_id=validated_data["publisher_id"])
        book.user.add(*validated_data["users"])
        return book

    def update(self, instance, validated_data):
        instance.title = validated_data.get("title", instance.title)
        instance.chapter = validated_data.get("w_chapter", instance.chapter)
        instance.pub_time = validated_data.get("pub_time", instance.pub_time)
        instance.publisher_id = validated_data.get("publisher_id", instance.publisher_id)
        if validated_data.get("users"):
            instance.user.set(validated_data.get("users"))
        instance.save()
        return instance

class BookView(APIView):
     def patch(self, request):
        print(request.data)
        book_id = request.data["id"]
        book_info = request.data["book_info"]
        book_obj = Book.objects.filter(pk=book_id).first()
        serializer = BookSerializer(book_obj, data=book_info, partial=True)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors)

三 ModelSerializer

现在我们已经清楚了Serializer的用法，会发现我们所有的序列化跟我们的模型都紧密相关~

那么，DRF也给我们提供了跟模型紧密相关的序列化器~~ModelSerializer~~

　　-- 它会根据模型自动生成一组字段

　　-- 它简单的默认实现了.update()以及.create()方法

定义一个ModelSerializer序列化器

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段

外键关系的序列化

注意：当序列化类MATE中定义了depth时，这个序列化类中引用字段（外键）则自动变为只读

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1
# depth 代表找嵌套关系的第几层

自定义字段

我们可以声明一些字段来覆盖默认字段，来进行自定制~

比如我们的选择字段，默认显示的是选择的key，我们要给用户展示的是value。

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)
    
    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1

Meta中其它关键字参数

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        depth = 1
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}

※ SerializerMethodField

外键关联的对象有很多字段我们是用不到的~都传给前端会有数据冗余~就需要我们自己去定制序列化外键对象的哪些字段~~

class BookSerializer(serializers.ModelSerializer):
    chapter = serializers.CharField(source="get_chapter_display", read_only=True)
    user = serializers.SerializerMethodField()
    publisher = serializers.SerializerMethodField()

    def get_user(self, obj):
        # obj是当前序列化的book对象
        users_query_set = obj.user.all()
        return [{"id": user_obj.pk, "name": user_obj.name} for user_obj in users_query_set]

    def get_publisher(self, obj):
        publisher_obj = obj.publisher
        return {"id": publisher_obj.pk, "title": publisher_obj.title}

    class Meta:
        model = Book
        fields = "__all__"
        # fields = ["id", "title", "pub_time"]
        # exclude = ["user"]
        # 分别是所有字段 包含某些字段 排除某些字段
        read_only_fields = ["id"]
        extra_kwargs = {"title": {"validators": [my_validate,]}}